The overall objective is to investigate the physiology, including behavior, of the adult female mosquito, especially the endocrine control of digestion, egg maturation, sexual behavior, host attraction, and biting. The effect of aging on certain physiological events will be investigated, as we have found that some reproductive processes are slower as the female ages. This has important epidemiological implications, because multiple blood-feeding during each gonotrophic cycle may become obligatory as the female ages. The ovary must be regarded as an endocrine organ, since it produces a hormone that stimulates vitellogenin synthesis by the fat body of blood-fed females, and, when the ovary retains a large enough number of eggs, it secretes a yolk inhibitor that suppresses development of less advanced oocytes. The relationship of these ovarian hormones to those secreted by the neurosecretory system and corpora allata (CA) will be investigated by ovarian transplantation and surgical ablation of the endocrine tissues. We will try to develop a bioassay for CA hormones in circulation and to determine the duration of the dependence of developing oocytes on both the CA hormone and the neurosecretory hormone. We will continue to study the rate of oocyte growth and the factors that influence the rate. The sequence of deposition of the various major constituents of yolk will be determined by chemical analysis. The effects of various physiological states (including different known nutritional levels, reproductive conditions, and parasite infections) on host attraction and biting by the female mosquito will be tested in a "host response chamber".